Frontward-rowing boat spanning angular oars having self-surfacing blades

ABSTRACT

Novel frontward-rowing crisscrossed boat-spanning angular oars having many unique advantages over usual oars are mounted on a portable crossbar anchored athwart the gunnels of a canoe, dinghy, skiff, or other rowable craft by thin, narrow bars rested lengthwise along the gunnels and bound to them by waterproof adhesive tape applied to the subjacent faces of the sidewalls of the craft. Streamlined carom-type shields insure against intercontact between oars and boat structure or accessories in case of extremely abnormal or excessive submergence. The blades resemble usual blades in being slab-shaped, yet unique buoyancy is achieved by cradling them in terminal portions of especially light-weight, rigid looms, plus use of low-density rigid cellular solid compositions or foams for their bodies; the buoyancy causing them to instantly and automatically rise to any predetermined degree of above-water emergence when released from immersive rowing force. Also, the blades are instantly replaceable by mere extraction through mouths in their cradles, followed by in-feeding therethrough of blades of selectedly different densities or heights. In addition, the buoyancy of individual blades can be lessened to any desired extent, and their long-time resistance to rowing stresses concomitantly supplemented, simply by in-feeding of elongate, rigid metal bars in horizontal disposition into narrow, vertically disposed, sleeve-like pockets in the blades, through tape-sealable mouths located, e.g., in their upper edges.

United States Patent 1191 Jewett SELF-SURFACING BLADES Harold A. Jewett, 5451 42nd St. N.W'., Washington, DC. 20015 22 Filed: July 27,1973

21 Appl. No.: 383,379

[76] Inventor:

[52] US. Cl. ll5/24.1, 416/74 [51] Int. Cl B63h 16/04 [58] Field of Search 115/21, 24.1, 24.2, 24.4, 1l5/24.5, 24.6, 19, 49; 416/69, 70, 71,72, 74; 9/2 A, 11 A [56] References Cited UNITED STATES PATENTS 998,153 7/1911 Birtels 1l5/24.4 1,281,642 10/1918 O'Hanlon 115/21 1,765,002 6/1930 Boyle et a1 115/24.5 2,367,222 1/1945 Kurtz 41'6/72 2,693,605 11/1954 Ber1ew.... 416/74 3,076,983 2/1963 Wait 416/71 3,086,492 4/1963 Hol1ey..... ll5/24.1 3,324,490 6/1967 Jewett 115/21 3,330,245 7/1967 Klabunde 1l5/24.2

FOREIGN PATENTS OR APPLICATIONS 133,368 3/1929 Switzerland [IS/24.1 402,412 10/1909 France l15/24.2

Primary Examiner-Trygve M. Blix Assistant Examiner-Galen L. Barefoot 5] Dec. 31, 1974 Novel frontward-rowing crisscrossed boat-spanning angular oars having many unique advantages over usual oars are mounted on a portable crossbar anchored athwart the gunnels-of a canoe, dinghy, skiff, or other rowable craft by thin, narrow bars rested lengthwise along the gunnels and bound to them by waterproof adhesive tape applied to the subjacent faces of the sidewalls of the craft. Streamlined caromtype shields insure against intercontact between oars and boatstructure or accessories in case of extremely abnormal or excessive submergence. The blades resemble usual blades in being slab-shaped, yet unique buoyancy is achieved by cradling them in tenninal portions of especially light-weight, rigid looms, plus use of low-density rigid cellular solid compositions or foams for their bodies; the buoyancy causing them to instantly and automatically rise to any pre-determined degree of above-water emergence when released from immersive rowing force. Also, the blades are instantly replaceable by mere extraction through mouths in their cradles, followed by iii-feeding therethrough of blades of selectedly different densities or heights. 1n addition, the buoyancy of individual blades can be lessened to any desired extent, and their long-time resistance to rowing stresses concomitantly supplemented, simply by in-feeding of elongate, rigid metal 7 bars in horizontal disposition into narrow, vertically disposed, sleeve-like pockets in the blades, through tape-sealable mouths located, e.g., in their upper edges.

21 Claims, 40 Drawing Figures PAHNIHJ W331 m4 SHEET 2 BF 4 FIGZZ.

PATENTEDBEBBI m4 7 5.857; 356

SHEET 3 BF 4 FIGH.

FRONTWARD-ROWING BOAT SPANNING ANGULAR OARS HAVING SELF-SURFACING BLADES This application relates to a boat mounting for frontward-rowing crisscrossed angular oars having selfsurfacing, self-leveling blades, said mounting comprising a crossbar for affixation athwart the gunnels of a rowboat, canoe, kayak, skiff, or other rowable craft by waterproof adhesive-tape clamping, as well as to said oars and blades themselves, and to novel accessories for them, including streamlined, caromtype shields disposed on said mounting for innocuous preclusion of intercontact between oars and boat structure or accessories, in case of extremely abnormal or excessive submergence.

The overall object of the invention is to minimize or eliminate the shortcomings of prior-art oars and their mountings by providing novel oars and novel mountings for them, comprising the following innovations and advantages:

i. Frontwardness of rowing via use of said crisscrossed angular oars;

ii. Instant mountability and demountability of said oars on any ordinary rowable craft via use of said crossbar and its accessories;

iii. Provision for the relatively slight lifting force involved in manipulation of said oars to be exerted in close juxtaposition to the oarsmans chest, rather than with his arms outstretched;

iv. Generous spacing-apart of the grip portions of the oars at all stages of their front-rear and reverse movement, in place ofthe conflicting or near-conflicting posture of said portions which characterizes prior-art oars generally;

v. Comfortable elevation of said grip portions throughout the return strokes as well as the power strokes of the oars, thereby avoiding the awkwardness incident to the exaggeratedly low posture of prior-art oars during their return strokes;

vi. Marked increase in efficiency of conversion of rowing energy by the oars, due to lessened obliquity of their blades at the beginning and end of power strokes of given lengths, as contrasted with the performance of prior-art oars in this regard;

vii. Marked decrease in breadth of water-area preemption by the oars, due to greater and more efficient lever use of the between-gunnels boat space, as contrasted with the smaller and far less efficient lever use of such space by prior-art oars;

viii. Instant, automatic self-surfacing or self-leveling of the oars to a pre-selected extent of above-water blade protrusion, following any interruption of immersive force upon them during use, as contrasted with the downwardly oblique total or near-total degree of blade submergence which characterizes usual prior-art blades following such interruption;

ix. Immediate pre-provision for a desired extent of such protrusion by simple insertion or extraction of weight rods (or weight-plus-stiffener rods) in horizontal disposition through mouths of thin, elongate pockets in the blades, as contrasted with the apparent absence of analogous such means in prior-art blades;

x. Unique visibility of the blades when their oars are floating freely at a distance from the boat or shore, due to upwardness of pitch achieved by pre-determined shift of the center of gravity of the oar in the direction of its handle; and

xi. Life-preserving utility of the oars due to the unique buoyancy of their blades and light-weight, advantageously hollow looms, particularly when extra large such blades have been installed in the loom cradles, with resultant in-effect reduction of the body density of a person clinging to them to a figure approximating, or even below the density of the water.

In the drawings, wherein all figures are to be understood as basically diagrammatic or schematic, and all expressions such as horizontal, upward, front, rear, etc. as being relative and approximate unless otherwise evident, to be more particularly described later on:

FIG. 1 is a rear elevation of the novel crossbar of the invention and associated accessories mounted across the gunnels of a 33-inch beam canoe and pivotally supporting a pair of the novel crisscrossed angular oars of the invention in position of use, with the oarsman facing away from the viewer, i.e., frontwardly;

FIG. 2 is a plan view of the oars of FIG. 1;

FIG. 3 is a rear elevation'detail similar to the central lower portion of FIG. 1 except that the canoe has been replaced by a 48-inch beam rowboat, the oarsmans seat is more elevated, and in auxiliary relatively long,

upwardly arched crossbar has been introduced as a support for the crossbar of FIG. 1;

FIG. 4 is an exploded side elevation detail depicting the process of adhesive-tape affixation of an elongatebar type clamp along a gunnel of the boat of FIG. I, to

thereby anchor its crossbar in position of use;

FIG. 5 is the same as FIG. 4 except that the anchoring has been completed;

FIG. 6 is a plan view detail of the parts shown in FIG. 5, plus the application of further adhesive tape crosswise of the clamp bar of FIGS. 5 and 4, and lengthwise of the cross-bar, to thereby fix the transverse position of the crossbar relative to the gunnels;

FIG. 7 is an end elevation detail showing the contingent functioning of either one of the carom-type arched shields appearing in FIG. I;

FIG. 8 is a left-end perspective detail showing the same functioning from a different viewpoint;

FIG. 9 is a perspective detail on enlarged scale of the pivot-end portion and certain adjacent parts of a righthand-operated loom such as that of FIG. 1;

FIG. 10 is a side elevation of the oarsman and a central portion of the parts appearing in FIG. 1, except that the pivot-pin block in FIG. 10 is affixed to the upper surface of the crossbar rather than to its under surface;

FIG. 11 is a bottom perspective of an end portion of a partially broken-away crossbar such as that of FIG. 9, but with clamp bars such as the one appearing in FIGS. 4-6 affixed to the bottom of a pivot-pin block carried by it;

FIG. 12 is the same as FIG. 11 except that the anchoring has been completed;

FIG. 13 is a plan.view detail of the oars and associated parts appearing in FIG. 1 except that the oars are in a far frontward posture and certain reserve or contingent guide structures have been added on the crossbar;

FIG. 14 couples a plan view detail with a side elevation detail of a prior-art structure relevant to a novel pivoting device contemplated for the oars of the invention;

section, of a novel pivoting device alternative to that of FIGS. l-16.

FIG. 18 is a plan view detail of the pivoting device of FIG. 17.

FIG. 19 is an exploded cross-sectional detail of a novel blade of the invention being fed downwardly FIG. 22 is a side elevation detail ofthe right end of the oar of FIG. 1, with the locus of its throat" indicated, said locus corresponding to that of the throat or inner blade end-to-loom connection of a usual oar;

FIG. 23 is aside elevation of a usual oar in position of use, except that its blade portion has been replaced by the novel cradle and buoyant blade of the invention, with the locus of its throat being depicted similarly'to the locus of the throat in FIG. 22, Le, as coinciding with the loom connection to the inner end of the blade;

FIG. 24 is an exploded plan view detail depicting in its lower part the blade of FIG. 23, in its middle part an elongate closure strip for the blade mouth, andin its upper part a supply of adhesive tape for afflxing said closure strip across the top surface of the blade;

FIG. 25 is a group of three identical side elevation diagrams of a cradled blade such .as that of FIGS. 23-24, showing the degree of immersion thereof when unweighted (as in the top diagram), the increased immersion thereof due to insertion of a first stiffener-weight bar into its pocket (as in the middle diagram), and the further increased immersion thereof after insertion of a second stiffener-weight bar (as in the bottom diagram);

FIG. 26 is aside elevation detail depicting the oar of FIG. 23 floating freely apart from the boat, the out-ofwater elevation of its blade end having been predetermined by loading its pivot, or handle, end to thereby shift its center of gravity handleward;

FIG. 27 is a side elevation detail showing the oars of both FIGS. 22 and 23 floating freely apart from the boat, with the aforesaid shifting of their. centers of gravity sufficiently handleward to cause them to float uprightly, blade end upward, thereby increasing their above-water visibility beyond that depicted in FIG. 26;

FIG. 28 is a group of side elevation details depicting the hand and wrist positions of an oarsman feathering one of the crisscrossed angular oars of the invention;

FIG. 29 is a group of side elevation details depicting modification of such oar to permit such style of feathermg;

FIG. 30 is essentially a reproduction of the prior-art FIG. 5 of applicants US. Pat. No. 3,324,490 showing the horizontally conflicting or near-conflicting handlemovem ent paths of conventional oars in use;

FIG. 31 is essentially a reproduction of FIG. 4 of applicants said patent showing the. generously horizontally spaced non-conflicting handle-movement paths of the criss-crossed oars of the invention;

FIG. 32 is a side elevation diagram showing the downward-cramping of said conventional oars on the return stroke;

FIG. 33 is a side elevation diagram corresponding to FIG. 32 except showing the generous upward spacing for the return stroke in the case of the crisscrossed cars of the invention;

FIG. 34 is a plan view diagram depicting the powerstroke length between a 45 starting posture of a backward-rowing oar such as that of FIG. 23 and a 45 ending posture thereof;

FIG. 35 is a plan view diagram depicting the corresponding, but much greater power-stroke length and therefore rowing-energy-conversion superiority of a frontward-rowing oar such as those. of FIG. 1 (they being exactly alike) having the same overall length as the oar of FIG. 34;

FIG. .36 illustrates the relativelyv great breadth of water area pre-empted by a pair of usual oars;

FIG. 37 illustrates the far less breadth of water-area pre-empted by crisscrossed angular oars of the invention having the same individual overall length as that of the oars of FIG. 36; such lessening in breadth being regarded as of major significance in situations such as encountered during canoe trips on narrow rivers, streams, canals and the like-in fact, wherever crowded boating conditions are apt to exist;

FIG. 38 is a side-elevational view of right-hand oar 9 of FIGS. 12 drawn to one-half the scale of those figures, with blades 26 per se omitted, but withschematic supports provided to effectuate the simulated posture of use specified inoriginal claim 8 of this application as filed;

FIG. 39 is the same as FIG. 38 except that the simulated posture of use in it is the one specified in original claim 7 of this application as filed;

FIG. 40 is a plan view of the parts appearing in FIG. 39.

Referring to the drawings in detail:

In FIGS. l-13 crossbar 1, supported on gunnels 2 and 3, is fixed in place by clamps 4 and 5 (5 being visible only in FIG. 13), which are anchored tightly to the boat by water-proof, pressure-sensitive adhesive tape 6, which itself is tightly adhered to both the inner and the outer surfaces (unnumbered) of the sidewalls of the boat. To insure against lateral displacement of the crossbar, adhesive tape 7 is tightly applied across the tops of clamps 4 and 5 plus adjacent portions of crossbar 1, as best seen in FIG. 6. Pivot-eye portion 8 of lefthand oar 9 is sleeved on oarlock pin 10, as shown in FIGS. 1, 3 and 13, said pin 10 being snugly secured by upright cylindrical oarlock socket 1 1 (depicted by dash lines in FIG. 3 and understood in FIGS. 1 and 13), lo-

cated at the center of pivot-pin block 12. Left-side counterparts of said members 8-12 will be readily apparent without numbering or in some instances with the same numbering.

Bearing in mind that the assembly of parts in FIG. 1 is symmetrical, and that all numbered parts to the right side of center plane 13 of the boat (said center plane being the vertical plane which includes the geometrical longitudinal axis of the boat) have identical counterparts to the left side thereof, said counterparts are readily identifiable and, unless otherwise appears, will be left unnumbered. Since the right-hand oar thus is identical with left-hand oar 9, as appears in the FIG. 1 at-rest position, it can be seen that each of their looms slopes obliquely upward from its pivot-eye portion to a point beyond said center plane and then, as at angle point 14, turns toward and then continues on until it meets transverse vertical plane 15 (which includes the centers of oarlock pin and its left-side counterpart) and then, as at angle point 16, turns waterward and remains in said plane throughout the rest of its length.

Reverting to crossbar 1, particularly as shown in FIGS. 7-8, arch-like carom-type shield 17 is affixed to pivot-pin block 18 (shown in FIG. 8 optionally united to the upper surface of crossbar 1, instead of the under surface thereof as is pivot-pin block 12 in FIGS. 1, 3 and 13) in position to present a rearwardly upwardly slanting portion 19 which will be glancingly contacted by loom portion 20 whenever the latter, due e.g., to stormy conditions, may happen to descend to such an extremely low elevation as would occasion such contact.

In FIG. 9 downwardly frontwardly curving leaf guide 21 is affixed to crossbar 1 in close proximity to and beneath reinforcing sleeve 22 of loomportion 23, to glancingly guide said sleeve 22 upwardly, in manner analogous to that of said portion 19 of shield 17, and

thereby insure against any chance of downward contacting of gunnel 3 (FIGS. 1, 3 and 13) by the righthand oar. (an optional variation of the positioning of said guide 21 (An shown in FIG. 13.)

A still further form of analogous guide is exemplified by surface 24 in FIGS. 1,3 and 13 (25 in FIG. 9), whose purpose is to insure against the highly unlikely yet conceivable contingency of hooking inter-engagement between outerportions of the looms and end portions of the crossbar.

Details of blades 26 and blade cradles 27, formed by terminal portions of the looms themselves, will be set out below.

Since the center-to-center distance between the oar lock pins in FIG. 1 is 36 inches, FIGS. 11-12 have been addressed to the situation where the crossbar needs to be mounted-on a boat having a 36-inch beam, in which case the presence of pivot-pin block 12 on the crossbar would preclude use of separate clamps such as 4 and 5 (FIGS. 4-6) for affixing the crossbar to the boat in precisely symmetrical relation thereto. Hence, corresponding clamps 28 and29 are integrated to the bottom of the overlying pivot-pin block 12, thereby permitting tape-clamping of their outward portions to the gunnels in the same manner as depicted in FIGS. 4-6 and 13.

FIG. 14 represents applicants recollection of an oarlock on a Hans Klepper Corporation boat displayed at a Boat Show at the DC. Armory in Washington, DC, Feb. 23. 1972, which applicant did not then 'and has not since seen or heard described. In said figure, verticalrather than to a conventional oar, and do not require the offsetting expedient shown in FIG. 14. In other words, said structures expand the width of the oar symmetrically rather than to one side only, besides permitto flank opposite faces 37 and 38 of pivot-pin block 39.

and thereby provide for horizontal rotative movement about vertical pivot pin 40 either'separately or concomitantly with up-down reciprocation about horizontal pivot pins 41 and 42, during use. g

In FIGS. 17-18 the parts correspond to those appearing in FIG. 9 except that welding metal used in their uniting is indicated at 43 and 44, top pivoteye piece 45 is rounded so that its upper surface slopes downwardly toward its union with the loom (effected by said welding metal 43), thereby permitting increased amplitude of upward swing by the loom during use, before being engaged by any overlying up-s top structure such, e.g. as nut 48, and the'upward flaring of the front and rear wall structures 46 and 47 of the pivot-eye piece 45 is more easily visible; said wall structures defining pivot eye 47a and being comprised of metal, as denoted by their form of sectionlining on FIG. 17. The spacing leeway between the nut 48 and the top of the pivot-eye piece 45, plus that between the front and rear bottom boundaries 49 and 50 of the eye, permits up-down reciprocation without need for horizontal pivot pins, i.e., via said leeway under the nut 48 at the top, and slight slippage of said boundaries 49 and 50 across the pivotpin block 51 at the bottom. And the horizontal reciprocation about pivot pin 52 is similar to that depicted in FIG. 16.

With regard to the above-mentioned unlimited dimensioning and strength of the parts permitted by the structures of FIGS. 15-16, it may be'added that, in the case of FIGS. 17-18, the increased overall crossdimensional area of the pivot-eye piece 45 not only exceeds the average overall cross-dimensional area of any other part of the boat-spanning portion of the loom, but also of the outboard part ofthe loom leading from said portion to the bladecarrying portion of the oar.

In FIGS. 19-21 inverted peripheral trough 53 in the rigid foam (e.g., expanded polystyrene having a bulk density of, say, about 3 pointsper cu. ft.) of the blade 26 may be formed by in-place foaming in a complementarily configurated mold,,or by searing with a complementarily dimensioned, heated round rod to appropriately convert the surface polymer into a tough, rigid skin, or, if desired, by purely mechanical means.

Because of the form-fit between the sides of the trough 53 and the converging upper surface 53a of the tubular-loom cradle 27 on and against which it snugly rests, no displacement will normally occur during use, unless by water-induced upward floating of the blade. And this is insured against by waterproof, pressuresensitive.adhesive-taping such as indicated in FIG. 21.

The significance of FIGS. 22 and 23 and the loci 54 of the throats appearing in them has already been pointed out, except for the matter of optimum extent of blade immersion. It has long been appreciated that substantial submergence of the upper edge of the blade during use tends to produce twists and twirls (Brit.

I 15,375 of 1913) so that an above-water posture of the entire length of said edge is desirable (US. Pat. No. 2,367,222, FIG. 8). But there has not been complete unanimity asto the optimum extent of such posture. Thus, page 127 of Aquatics Handbook by M. A. Gabrielsen et al., Prentice-Hall, Inc., 1960, states: About 2/3 or 3/4 of the blade should enter the water;" page 97 of Boating from Bow to Stern by .l. P. Kenealy,

Dodd, Mead and Co., 1966, advises that the blades I sirable, .unless on account of resultantly increased air or wind pressure during stroking or feathering, or why deeper immersion, if desired, might not be practiced, with extra-large slab-shaped blades, to thereby achieve more powerful and therefore faster rowing.

In such case, the novel self-leveling action of a blade of the invention can readily be provided for by the expedient illustrated in FIGS. 24 and 25. In said figures,

, upwardly open mouth 55 of narrow, elongate pocket 56 of upright-in-use blade 26 seated in cradle 27 is disposed for reception of one or more weight, or stiffener-' plus-weight, bars 57 into the pocket 56, so that it will rest lengthwise on the bottom 58 thereof. Of course, a shorter pocket and differently shaped weights could be used, but it is preferred to employ elongate weights (either singly or in multiples) comprising considerable vertical dimension, so as to thereby supplement the in herent rigidity of the blade and its skin and/or other facing against undue flexure in use. Such rigidity per se can be made very substantial merely by applying the sear treatment of the flat surfaces of the blade in manner such as mentioned in connection with FIGS. 19-21 above, or by in-place foam-molding methods well known to workers in that art. By way of illustration, it may be remarked that if the blade be inches in length and IV inch wide (at the water level) a bar weighing 1/2 pound will produce about 1 inch of submergence, since the volume of displaced water will be 15 cu. in. and therefore have a weight of about /9 pound.

Sealing of the mouth 55 of the pocket 56 is accomplished by affixing closure element 59 with waterproof adhesive tape 60 applied across its top and down along each subjacent side surface of the blade.

In FIG. 26 oar 61 corresponds to a usual oar except for its novel blade cradle 27 and blade 26, and the fact that its center of gravity has been located sufficiently handleward for its tip 62 to be elevated entirely above the water level, thereby giving it improved visibility as compared with tips of floatable conventional oars when lost in the water. Preferably the elevation of the tip 62 will be such that an above-water vertical distance equal to at least a, 5/4, twice or more the maximum thickness of the blade will underlie said elevation. Of course, as saidhandleward shifting. of the center of gravity is increased, the counterclockwise rotation of the blade will speed up until it reaches the optimum posture shown in FIG. 27.

Due to necessary (for strengthlweight of the pivotcontacting portion 63 of the angular oar 9 in said figure, the free-floating posture of such oar and its tip 62-a will generally be as depicted therein.

In applying said test, the tip of the oar is taken to be the point on the blade end farthest from the pivot, or handle, end. I

In FIG. 28, A represents the posture 64 of an oarsmans hand and wrist at the end of a power stroke with one of the novel oars 9 of the invention, B said posture during lifting and feathering of the oar, and C said posture at the conclusion thereof; while D represents said posture following frontward manipulation of the oar preparatory to a new power stroke, E said posture during lowering and de-feathering of the'oar, and F said posture at the beginning of the new power stroke.

The optional structuring shown in FIG. 29 adapts the novel crisscrossed oars of the invention to feathering in the manner depicted by FIG. 28. Thus, an inner splice tube or member 65 (shown in the bottom portion of FIG. 29) is used, on which both sections 66 and 67 of a two-section loom are sleeved, the pivotward section 66 being immovably affixed to it by rivet 68, and cornthe posture indicated by the dash lines at the lower right bottom of said top portion. Next, when the D position is reached, he feeds the tooth 70 back into said recess 69 and thereupon rotates it into reengagement with said wall 72, for the start of a new power strokeall as depicted by the arrows and dash lines in FIG. 29.

Endward displacement of the slideable bladeward section 67 is precluded by the lug 73 on the splice tube 65, said lug being positioned to engage the left end 74 of the horizontal opening 75 in the bladeward section 67, in the event of excessive outward movement thereof during use.

The above explained significance. of diagrammatic FIGS. 30-33 in respect to abundance of the available space for uncramped and comfortably elevated hand movements during manipulation of the crisscrossed oars of the invention, i.e., as contrasted with the restricted and cramped hand-movement space in the case of usual oars, is repeated here.

The overall lengthof each of the oars in FIGS. 34-37 is 5 feet.' No numeralizing of their parts appears needed, in view of the general description already made of themhereinabove.

FIGS. 34 and 35 each shows an oar in position of use with its blade at a frontward 45-angle stroke-starting posture, as well as the same blade in a 45-angle strokeending posture; the oar of FIG. 34 being a conventional (lever-of-the-first-kind) oar, while that of FIG. 35 is a crisscross angular (lever-of-the-third-kind) oar of the invention. By "lever-of-the-third-kind," as used herein and in the appended claims, is meant any lever wherein the locus of the effort is between the locus of the load and the locus of the fulcrum, as, e.g., in the case of a broom or a canoe paddle; the blade-pushed water being considered as the load for purposes of the lexicography of this application and its appended claims, even though some analysts (believed to be in the minority) have preferred to characterize the boat (via its oarlock socket or thole pin) as the load, and the bladepushed water as the fulcrum, which, -it may be noted, would make an ordinary oar, as a matter of semantics, a lever of the second kind (analogous to a wheelbarrow) rather than a lever of the first kind as denominated herein. It is notable that the stroke length S in FIG. 34 is only feet, while that in FIG. 35 is 7 3/4,

feet (about 50 percent greater).

FIGS. 36 and 37 each shows a pair of the same oars as respectively shown in FIGS. 34-35, but pivoted on the gunnels of a 36 inch-beam boat; the breadth of water area pre-emption P by the conventional pair (FIG. 36) being I I feet, as contrasted with the mere 8 feet of such pre-emption by the crisscrossed angular oars of the invention (FIG. 37).

In FIGS. 38-40, oar 9 is identical with each oar 9 of FIGS. 1-2, except for being drawn to only one-half their scale and omitting blades 26 per se.

In FIG.- 38 pivot-eye portion 8 of said oar is resting on support 76 at a point (unnumbered per se) having elevation 77, while the lowermost point 78 of the blade-carrying portion (27 on FIG. 1) of said oar is resting on support 79 at elevation 80, the latter elevation being 18 inches lower than said elevation 77.

In FIG. 39 the situation is the same as in FIG. 38 except that said 18 inches has been reduced to 12. inches and context in original claim 7 (line 9) and original claim 8 (line 2) of this application as filed; said 12 inches serving to typify, of course, a relatively heavily loaded and consequently more submerged boat, and said l 8 inches," in contrast, a relatively lightly loaded and consequently less submerged boat.

It will be noted that the loom (unnumbered per se) of said oar 9 in said FIGS. 38-40 comprises a segment 82 which begins at the upright axis 83 of said pivot-eye portion 8 and (as viewed in side elevation on FIGS. 38-39) slopes upwardly outwardly at an acute angle with the horizontal to a turning point 84, plus a subsequent segment 85 which begins at said turning point 84 and slopes upwardly outwardly to a subsequent turning point 86 lying in the imaginary upright plane 87 (seen only as a line [FIG 40]) which includes said upright axis 83 and the aforesaid lowermost point 78 of the outer terminal blade-carrying portion of oar 9. It will additionally be apparent (from FIG. 40) that said segment 82 is longer than said subsequent segment 85 and diverges away from said upright plane 87; also, that said subsequent segment 85 converges toward and into coincidence with said upright plane 87 at said subsequent point of turning 86, the latter point occurring, as appears in FIGS. 1-2, inboard of the right-side gunnel 3 of the 33-inch-beam canoe of FIG. 1.

It will further be noted, in regard to said oar 9 and its identical companion oar in FIGS. l-2, that each consists of a self-surfacing blade-carrying portion and a loom, said loom having a pivot-contacting inner terminal portion, a boat-spanning portion, and an outer portion (unnumbered per se, but exemplified by the portion of oar 9 to which its lead lines are directed on FIGS. 38-40 as well as on FIGS. l-2). Also, Whereas segment 82 embodies a rearward component of direction and subsequent segment 85 a frontward component of direction, as respectively shown on FIG. 40, the identical companion oar appearingin FIGS. l-2 embodies a'frontward, rather than rearward, component of direction in its segment (unnumbered) corresponding to said segment 82, and a rearward, rather than frontward, component of direction in its subsequent segment (unnumbered) corresponding to subsequent segment 85 of the oar of FIGS. 38-40. This interrelationship between the two mutually identical oars of FIGS. l-2 sharply differentiates them from the oars of FIGS. 1-3 of applicants US. Pat. No. 3,324,490, since the oars of that patent are not mutually identical, and

be observed that the bisection of the blade portions and adjoining outer loom portions of both of the oars of the present invention by the transverse upright plane 15, as shown on FIG. 2 hereof, with the unique advantages reflected thereby, is foreign to the geometrical interrelationship of the mutually non-identical oars of said US. Pat. No. 3,324,490.

Along with the aforesaid geometrical differences between said oar 9 and either of the oars in FIGS. l-3 of said patent, it may still further be mentioned that said oar 9 of this application, by reason of its improved dimensioning and contouring, per se effects substantial novel economies in weight, lineal oar length, overall oar length, material, cost and manipulability, as compared with either oar of said US. Pat. No. 3,324,490,.

in addition to better facilitating avoidance of intercontact with either an underlying gunnel of a boat during use or the loom of another oar paired with it for frontward rowing.

With regard tothe term loom as used herein, although dictionary definitions exist wherein its meaning would be restricted to the inboard portions of oars, it is believed that the concensus of dictionary definitions apply the term to the entire extent of the oars shaft, exclusive only of the blade-carrying portion of the oar. As already made apparent hereinabove, it is this latter meaning which is intended herein, so that language referring to the blade-carrying ,cradles of the novel blades of this invention as being constituted by terminal portions of its tubular looms is not to be construed as enlarging the aforesaid meaning of the term loom.

Referring again to the crossbar of FIGS. l-13, its novel tape-fastening makes it readily eligible for use (optionally with obvious variations) as a thwart-type support for any desired objects including, e.g., seating of passengers.

Particularly appropriate illustrations of suitable pressure-sensitive adhesive tapes for said fastening are exemplified, e.g., by Scotch" (3M Company) Industrial Tape Nos. 890 or 870.

Should a particular tape happen to prove waterpermeable to more than a negligible extent, it could of course be protected by a thin overlay of rubber-type tape such as the tapes commonly available in hardware stores under the designation electrical tapes.

It may be remarked that preliminary application of a relatively thick double-stick" tape to the top of the gunnels of a boat, before placing the clamp bars of FIGS. 4-6 on them, is an optional expedient.

When the crossbar of FIGS. 1-13 is used for the purposes directly contemplated in those figures, the affixation of the pivot-pin block may be by any desired means, e.g., gluing with waterproof epoxy-type glues and/or bolting.

When the pin blocks are affixed to the upper surface of the crossbar, as in FIG. 12, and given suitable height, the crossbar becomes useful as a mounting for lever-ofthe-first-kind oars which may comprise oarlock sockets such e.g., as the one shown in FIG. 14, without difficulty arising from intercontact with the crossbar during the return stroke. In such case, the cramped-space inconveniences'depicted in FIGS. 30-33 will be obviated.

I And in addition, lengthening of the crossbar will make inch 0D. or 7/8 inch OD. and 0.065 inch wall thickness has been found satisfactory, particularly when its angles have been imparted by cold-bending so as topreserve the temper of the tubing.

Resistance to sea water is enhanced by anodizing; but alternatively, alloys of comparable strength and rigidity, together with extremely high inherent resistance to sea water, are understood to be presently available.

Said 606l alloy is excellently suitable for the cradlesegment end of the oars of the invention, by virtue of its toughness and ruggedness, when such segment is used for pushing the craft from shore or for making pushing contact with the bottom of a stream or lake.

A' unique advantage of making the subject oars exactly alike is that-it enables a person seated oppositely to the oarsman to take over" the rowing from him, withoutany shifting of position by either. Also,should any overstressing occur during use of the oars, i.e., such as would give rise to incipient distortion, mere switching of the oars would readily correct it via the wellknown phenomenon of work-hardening."

Blade-space," as used herein and in the appended claims, means the space enclosed within an imaginary flexible film wrapped tightly around all portions of the entire blade, inclusive of its cradle,

Should collapsibility of the subject oars be desired, that of course may be accomplished by segmentation in accordance with techniques well known in the art; or an internal splice tube analogous to tube 65 in FIG. 29 but caged in place, e.g., by bends in the segments of the loom to be joinable, may be employed. with such segments inter-united, e.g., by longitudinal laps of waterproof adhesive tape, such laps optionally being reenforced by circumferential laps in turn applied to them.

Strengthening tubular inserts can, of course, be used as desired, in any portions of the looms, e.g., within a portion such as the loom portion 23 appearing in FIG. 9.

In connection with the optional hollowness of the tubular looms, it will be noted that internal reenforcement with rigid foam is available, as well as external re-enforcement with, e.g., fiberglass-resin compositions in accordance with US. Pat. No. 3,561,760 (col. 2).

As for hollow blades of the priorart, it may be remarked that if they spring a leak their buoyancy is gone; whereas with expanded polystyrene or polyurethane, e.g., abrasion or gouging of the same causes no such trouble, owing not only to the almost total water-impermeability thereof, but also to the relative simplicity of repairing the blade in such case.

Production of the tough, rigid skin contemplated for the water-engaging surfaces of the blade, as spoken of elsewhere herein, can be carried out by methods pointed out on page 169 of the Journal of Cellular Plastics, Vol. 6, No. 4 (July-August, 1970), in the course of an article entitled A New Generation of Structural Foam Polymers by R. L. Grieve et al., (Upjohn Co. Research Labs., North Haven, Conn), wherein it is stated that The applications of integral skin foam molding for structural and decorative parts are unlimited And on page 167 (in the course of the same article) the statement appears that The integral skin foam process leads naturally to the concept of very stiff (high modulus) integrated parts. The outer surface and the reinforcing configuration may be achieved in a single molding," with stiffness of course enhanced by ribbing wherever possible.

The wide variety of cellular solids eligible for use in the bodies of the blades-particularly when internal structures embedded via pre-molding'or pre-foaming processes are to be provided, e.g., structures such as the pockets in FIGS. 2425 and the peripheral recesses of FIGS. 9 and l92lwill become evident on inspection of The Survey of Foamed Plastics appearing on pages 294296 of The Modern Plastics Encyclopedia for 1965 which accompanied the issue of Modern Plastics (published by McGraw-Hill, Inc.) for Sept., 1964, as well, of course, as in the highly revealing US. patent literature on the subject.

Supplementing the introductory statement of advantages of the invention appearing hereinabove, it may be remarked that by relieving oarsmen of having to keep looking over their shoulders to see where they are going, the new oars are uniquely suited to general use by all persons preferring rowing to motor power, whether for exercise, quietness, economy, ecology, or otherwise, and even more so to special use by all persons employing rowboats for such purposes as sneak approaches in hunting, fishing, exploring, and picturetaking; tender service over shallow, swampy, obstruction-ridden waters; activites potentially involving rescue or other emergency operations; rental to noveltyseekers at amusement park or playground lakes and ponds; and physical therapy at recreation, convalescent and rehabilitation centers. Also, in reduced sizes on small, easily maneuverable boats, the new oars open up an unlimited range of water sports, games, contests,

and group exercises hitherto automatically ruled out by risks of collision and other mishaps inherent in the centuries-old backward-facing rowing done with usual oars, but eliminated by the frontward-facing rowing done with the new oars.

herein is being claimed in divisional application. Ser. No. 45l,563 filed Mar. 15, 1974.

What is claimed is:

1. A rowing oar formed of metal tubing and terminating in a blade-end portion comprising a throat and a cradle segment having an upwardly divergent crosssectional contour,

Said blade-end portion also comprising a slab-shaped blade whose thickness is both less than its breadth and less than its length,

Said blade being carried by said cradle segment,

The outer terminal portion of such cradle segment consisting of an upwardly angled extension of the bottom portion of such cradle segment,

The throat end of such cradle segment and the upper end of said outer terminal portion constituting a cradle mouth for reception of said blade when fed directly there-through into seating engagement on said cradle segment,

The throatward. bottom and outward edge surfaces of said blade containing a peripheral trough defined by walls complementary to said upwardly convergent cross-sectional contour,

Said blade being secured in place by close juxtaposition of said walls to side portions of said bottom portion of said cradle segment.

2. The oar of claim 1 wherein:

At least one-third of the blade-space occupied by said blade is occupied by water-impermeable, rigid cellular solid havinga bulk density within the range of 25 to 0.5 pounds per cubic foot.

3. The oar of claim 2 wherein:

Said cellular solid comprises an expanded organic polymer.

4.'The oar of claim 3 wherein:

Said polymer comprises polystyrene.

5. The oar of claim 3 wherein:

Said polymer comprises polyurethane.

6. The oar of claim 3 wherein:

A face of said blade is constituted by a rigid skin comprising said polymer in unfoamed state.

7. The oar of claim 6 in which said blade comprises:

open-mouthed cradle formed by a terminal portion.

of said tube,

Said blade comprising spaced-apart peripheral walls defining a longitudinal trough having a transverse configuration complementary to that of said tube,

Said blade being held against upward displacement by waterproof adhesive tape encompassing a bottom portion of said cradle,

Said blade being held against lateral, endward and downward displacement by the confining effect of said cradle on said blade.

9. The combination of claim 8 wherein said tube coristitutes the loom of a lever-of-the-first-kind oar,

A handleward portion of said oar being so weighted that when said oar is floating freely in calm water the tip of its blade end protrudes above the water a distance equal to at least one-half the maximum thickness of the blade, 4

10. A feathe'rable oar for use in rowing, said oar being a lever of the third kind when in position of use and comprising a pivotward portion and a bladeward portion in axial co-alinement;

Said oar comprising an inner splice member about which said portions are sleeved;

Said pivotward portion being immovably joined to portion about said splice member via engaging said tooth; and Said splice member being provided with a lug disposed to block undesired outward movement of said bladeward portion via engaging said transverse wall surface; 1 Whereby feathering of said bladeward portion is made feasible via withdrawing said tooth from said first peripheral opening in advance of the return stroke, and upright posturing of the oars blade may be maintained via reinsertion of said tooth into said first peripheral opening in preparation for the power stroke. I 11. A frontward-rowing angular oar which-acts as a boat-spanning lever of the third kind during use when pivoted adjacent one gunnel of a boat with its blade end located in water beyond the opposite gunnel of the boat, which oar comprises:

A loom having a pivot-contacting inner terminal portion adapted for horizontal reciprocation about an upright pivot axis during use, and

A blade-carrying outer terminal portion which is .upright during such reciprocation and has a hereinafter identified lowermost point,

Said loom-as seen in side elevational view of said oar with said pivot-contacting terminal portion resting motionlessly on a first support at a point having a first elevation-and the lowermost point of said blade-carrying portion resting motionlessly on a second support at a second elevation, said second elevation being lower than said first elevation and both said points being included in a common imaginary upright plane-comprising, as seen in plan view of said oar, i

A segment which begins at said pivot-contacting inner terminal portion and diverges away from said upright plane at an acute angle to a point of turning; said loom also comprising i A subsequent segment which, beginning at said point of turning, converges toward said upright plane and to a subsequent point of turning, which subsequent point of turning occurs inboard of said opposite gunnel when said boat is a 33-inch-beamcanoe; said loom further comprising A more subsequent segment which, beginning at said subsequent point of turning, makes an outward angle relative to said subsequent segment and continues to said blade-carrying outer terminal portion of said oar,

Said first-mentioned segment being longer than said subsequent segment and following an upwardly sloping path, as seen in said side elevational view of said oar, and

Said subsequent segment being more nearly perpendicular to said upright plane than said firstmentioned segment, as seen in said plan view of said oar.-

12. A pair of boat-spanning angular oars for use in frontward rowing, each of which oars conforms to the requirements of claim 11, wherein, when said oars are respectively pivoted at loci adjacent opposite gunnels of a boat having a beam of 33 inches, said loci being located in a common imaginary upright plane that is perpendicular to the center plane of said boat and said oars being disposed directly crosswise of the boat and pointing in exactly opposite directions with their said bladecarrying outer terminal portions floating freely and motionlessly in a body of water surrounding said boat,

The above-stated diverging of said first-mentioned segment is rearward in the case of one said oar and frontward in the case of the other said oar, and

The above-stated converging of said subsequent segment is frontward in the case of said one said oar" and rearward in the case of said other said oar.

13. the oar of claim 11, wherein:

Said pivot-contacting inner terminal portion of said loom includes wall structure defining a pivot eye having an axis which is upright during use, and

Said second elevation is 12 inches lower than said first elevation.

14. The pair of oars of claim 12 wherein:

Said oars are mutually identical.

15. The oar of claim 13, wherein:

Saidsubsequent segment follows an upwardly sloping path, as seen in said side elevational view of said oar. and

Said wall structure comprises metal.

16. The oar of claim 15, wherein: I

Said blade-carrying outer terminal portion comprises a blade which is slab-shaped and self-surfacing in use, and,

The overall density of said oar is less than that of water.

17. The oar of claim 16, wherein:

At least one-eighth of the side surface of each face of said blade protrudes above the water when the buoyant force ofa body of calm water in which said blade-carrying portion is floating is substituted for said second support.

18. The oar of claim 17, wherein:

At least one-third of the side surface of each face of said blade protrudes above the water when the buoyant force ofa body of calm water in which said blade-carrying portion is floating is substituted for said second support.

19. The oar of claim 18, wherein:

Said pivot eye has upwardly diverging front and rear metallic walls having mutually opposed wall surfaces extending transversely of said loom and is adapted for receiving and for horizontal rotative reciprocation about, a vertically disposed pivot pin during use.

20. The oar of claim 18, wherein:

Said pivot-contacting inner terminal portion is a metallic block containing an upright. recess disposed for permitting horizontally rotative reciprocation of said block about an upright pivot pin during use;

Said oar also comprising bifurcate metallic arms flanking opposite faces of said block and containing horizontal recesses;

Said block holding horizontal pivot pins respectively protruding therefrom and into said horizontal recesses;

Up=down reciprocation of said oar about said horifirstelevation.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PATENT NO. 3,857,356 DATED December 31, 19711.

r v (5) Harold A. Jewett It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In column 2, line 25, "in" should be ---an--- In column 5, line 31, "an" should be --An--.

In column 5, line 32, "(An" should be --i.s--;

In column 13, line 7, "divergent" should be -c onvergent--.

Signed and Sealed this twenty-second Day Of July l975 [SEAL] Arrest:

RUTH C. MASON C. MARSHALL DANN Alffllini ffi Commim'oner of Parents and Trademarks 

1. A rowing oar formed of metal tubing and terminating in a blade-end portion comprising a throat and a cradle segment having an upwardly divergent cross-sectional contour, Said blade-end portion also comprising a slab-shaped blade whose thickness is both less than its breadth and less than its length, Said blade being carried by said cradle segment, The outer terminal portion of such cradle segment consisting of an upwardly angled extension of the bottom portion of such cradle segment, The throat end of such cradle segment and the upper end of said outer terminal portion constituting a cradle mouth for reception of said blade when fed directly there-through into seating engagement on said cradle segment, The throatward, bottom and outward edge surfaces of said blade containing a peripheral trough defined by walls complementary to said upwardly convergent cross-sectional contour, Said blade being secured in place by close juxtaposition of said walls to side portions of said bottom portion of said cradle segment.
 2. The oar of claim 1 wherein: At least one-third of the blade-space occupied by said blade is occupied by water-impermeable, rigid cellular solid having a bulk density within the range of 25 to 0.5 pounds per cubic foot.
 3. The oar of claim 2 wherein: Said cellular solid comprises an expanded organic polymer.
 4. The oar of claim 3 wherein: Said polymer comprises polystyrene.
 5. The oar of claim 3 wherein: Said polymer comprises polyurethane.
 6. The oar of claim 3 wherein: A face of said blade is constituted by a rigid skin comprising said polymer in unfoamed state.
 7. The oar of claim 6 in which said blade comprises: An elongate, thin pocket having a mouth opening in the upper edge surface of said blade, Said mouth being adapted for reception of weight-contributing metal bars to provide for increased self-immersion of said blade during use.
 8. In combination: A rowing oar having a loom constituted by a rigid metal tube, A buoyant, slab-shaped blade seated in an upwardly open-mouthed cradle formed by a terminal portion of said tube, Said blade comprising spaced-apart peripheral walls defining a longitudinal trough having a transverse configuration complementary to that of said tube, Said blade being held against upward displacement by waterproof adhesive tape encompassing a bottom portion of said cradle, Said blade being held against lateral, endward and downward displacement by the confining effect of said cradle on said blade.
 9. The combination of claim 8 wherein said tube constitutes the loom of a lever-of-the-first-kind oar, A handleward portion of said oar being so weighted that when said oar is floating freely in calm water the tip of its blade end protrudes above the water a distance equal to at least one-half the maximum thickness of the blade.
 10. A featherable oar for use in rowing, said oar being a lever of the third kind when in position of use and comprising a pivotward portion and a bladeward portion in axial co-alinement; Said oar comprising an inner splice member about which said portions are sleeved; Said pivotward portion being immovably joined to said splice member and said bladeward portion being rotatively disposed about said splice member; Said pivotward portion comprising a first peripheral opening bounded by a longitudinal wall portion and said bladeward portion comprising a second peripheral opening bounded by a transverse wall portion; Said bladeward portion also comprising a peripheral tooth disposed for longitudinal reciprocative movement into and from said first peripheral opening via sliding of said bladeward portion along said splice member; Said longitudinal wall surface being disposed to block undesired rotative movement of said bladeward portion about said splice member via engaging said tooth; and Said splice member being provided with a lug disposed to block undesired outward movement of said blAdeward portion via engaging said transverse wall surface; Whereby feathering of said bladeward portion is made feasible via withdrawing said tooth from said first peripheral opening in advance of the return stroke, and upright posturing of the oar''s blade may be maintained via reinsertion of said tooth into said first peripheral opening in preparation for the power stroke.
 11. A frontward-rowing angular oar which acts as a boat-spanning lever of the third kind during use when pivoted adjacent one gunnel of a boat with its blade end located in water beyond the opposite gunnel of the boat, which oar comprises: A loom having a pivot-contacting inner terminal portion adapted for horizontal reciprocation about an upright pivot axis during use, and A blade-carrying outer terminal portion which is upright during such reciprocation and has a hereinafter identified lowermost point, Said loom-as seen in side elevational view of said oar with said pivot-contacting terminal portion resting motionlessly on a first support at a point having a first elevation and the lowermost point of said blade-carrying portion resting motionlessly on a second support at a second elevation, said second elevation being lower than said first elevation and both said points being included in a common imaginary upright plane-comprising, as seen in plan view of said oar, A segment which begins at said pivot-contacting inner terminal portion and diverges away from said upright plane at an acute angle to a point of turning; said loom also comprising A subsequent segment which, beginning at said point of turning, converges toward said upright plane and to a subsequent point of turning, which subsequent point of turning occurs inboard of said opposite gunnel when said boat is a 33-inch-beam canoe; said loom further comprising A more subsequent segment which, beginning at said subsequent point of turning, makes an outward angle relative to said subsequent segment and continues to said blade-carrying outer terminal portion of said oar, Said first-mentioned segment being longer than said subsequent segment and following an upwardly sloping path, as seen in said side elevational view of said oar, and Said subsequent segment being more nearly perpendicular to said upright plane than said first-mentioned segment, as seen in said plan view of said oar.
 12. A pair of boat-spanning angular oars for use in frontward rowing, each of which oars conforms to the requirements of claim 11, wherein, when said oars are respectively pivoted at loci adjacent opposite gunnels of a boat having a beam of 33 inches, said loci being located in a common imaginary upright plane that is perpendicular to the center plane of said boat and said oars being disposed directly crosswise of the boat and pointing in exactly opposite directions with their said blade-carrying outer terminal portions floating freely and motionlessly in a body of water surrounding said boat, The above-stated diverging of said first-mentioned segment is rearward in the case of one said oar and frontward in the case of the other said oar, and The above-stated converging of said subsequent segment is frontward in the case of said ''''one said oar'''' and rearward in the case of said ''''other said oar.''''
 13. the oar of claim 11, wherein: Said pivot-contacting inner terminal portion of said loom includes wall structure defining a pivot eye having an axis which is upright during use, and Said second elevation is 12 inches lower than said first elevation.
 14. The pair of oars of claim 12 wherein: Said oars are mutually identical.
 15. The oar of claim 13, wherein: Said subsequent segment follows an upwardly sloping path, as seen in said side elevational view of said oar, and Said wall structure comprises metal.
 16. The oar of claim 15, wherein: Said blade-carrying outer terminal portion comprises a blade which is slab-shaped aNd self-surfacing in use, and, The overall density of said oar is less than that of water.
 17. The oar of claim 16, wherein: At least one-eighth of the side surface of each face of said blade protrudes above the water when the buoyant force of a body of calm water in which said blade-carrying portion is floating is substituted for said second support.
 18. The oar of claim 17, wherein: At least one-third of the side surface of each face of said blade protrudes above the water when the buoyant force of a body of calm water in which said blade-carrying portion is floating is substituted for said second support.
 19. The oar of claim 18, wherein: Said pivot eye has upwardly diverging front and rear metallic walls having mutually opposed wall surfaces extending transversely of said loom and is adapted for receiving, and for horizontal rotative reciprocation about, a vertically disposed pivot pin during use.
 20. The oar of claim 18, wherein: Said pivot-contacting inner terminal portion is a metallic block containing an upright recess disposed for permitting horizontally rotative reciprocation of said block about an upright pivot pin during use; Said oar also comprising bifurcate metallic arms flanking opposite faces of said block and containing horizontal recesses; Said block holding horizontal pivot pins respectively protruding therefrom and into said horizontal recesses; Up-down reciprocation of said oar about said horizontal pivot pins during use being thereby provided for, independently of the aforesaid horizontally rotative reciprocation.
 21. The oar of claim 18, wherein: Both said more subsequent segments and said blades are longitudinally bisected by said upright plane, and Said second elevation is 18 inches lower than said first elevation. 